uio.h

  1/* SPDX-License-Identifier: GPL-2.0-or-later */
  2/*
  3 *	Berkeley style UIO structures	-	Alan Cox 1994.
  4 */
  5#ifndef __LINUX_UIO_H
  6#define __LINUX_UIO_H
  7
  8#include <linux/kernel.h>
  9#include <linux/mm_types.h>
 10#include <linux/ucopysize.h>
 11#include <uapi/linux/uio.h>
 12
 13struct page;
 14struct folio_queue;
 15
 16typedef unsigned int __bitwise iov_iter_extraction_t;
 17
 18struct kvec {
 19	void *iov_base; /* and that should *never* hold a userland pointer */
 20	size_t iov_len;
 21};
 22
 23enum iter_type {
 24	/* iter types */
 25	ITER_UBUF,
 26	ITER_IOVEC,
 27	ITER_BVEC,
 28	ITER_KVEC,
 29	ITER_FOLIOQ,
 30	ITER_XARRAY,
 31	ITER_DISCARD,
 32};
 33
 34#define ITER_SOURCE	1	// == WRITE
 35#define ITER_DEST	0	// == READ
 36
 37struct iov_iter_state {
 38	size_t iov_offset;
 39	size_t count;
 40	unsigned long nr_segs;
 41};
 42
 43struct iov_iter {
 44	u8 iter_type;
 45	bool nofault;
 46	bool data_source;
 47	size_t iov_offset;
 48	/*
 49	 * Hack alert: overlay ubuf_iovec with iovec + count, so
 50	 * that the members resolve correctly regardless of the type
 51	 * of iterator used. This means that you can use:
 52	 *
 53	 * &iter->__ubuf_iovec or iter->__iov
 54	 *
 55	 * interchangably for the user_backed cases, hence simplifying
 56	 * some of the cases that need to deal with both.
 57	 */
 58	union {
 59		/*
 60		 * This really should be a const, but we cannot do that without
 61		 * also modifying any of the zero-filling iter init functions.
 62		 * Leave it non-const for now, but it should be treated as such.
 63		 */
 64		struct iovec __ubuf_iovec;
 65		struct {
 66			union {
 67				/* use iter_iov() to get the current vec */
 68				const struct iovec *__iov;
 69				const struct kvec *kvec;
 70				const struct bio_vec *bvec;
 71				const struct folio_queue *folioq;
 72				struct xarray *xarray;
 73				void __user *ubuf;
 74			};
 75			size_t count;
 76		};
 77	};
 78	union {
 79		unsigned long nr_segs;
 80		u8 folioq_slot;
 81		loff_t xarray_start;
 82	};
 83};
 84
 85typedef __u16 uio_meta_flags_t;
 86
 87struct uio_meta {
 88	uio_meta_flags_t	flags;
 89	u16			app_tag;
 90	u64			seed;
 91	struct iov_iter		iter;
 92};
 93
 94static inline const struct iovec *iter_iov(const struct iov_iter *iter)
 95{
 96	if (iter->iter_type == ITER_UBUF)
 97		return (const struct iovec *) &iter->__ubuf_iovec;
 98	return iter->__iov;
 99}
100
101#define iter_iov_addr(iter)	(iter_iov(iter)->iov_base + (iter)->iov_offset)
102
103static inline size_t iter_iov_len(const struct iov_iter *i)
104{
105	if (i->iter_type == ITER_UBUF)
106		return i->count;
107	return iter_iov(i)->iov_len - i->iov_offset;
108}
109
110static inline enum iter_type iov_iter_type(const struct iov_iter *i)
111{
112	return i->iter_type;
113}
114
115static inline void iov_iter_save_state(struct iov_iter *iter,
116				       struct iov_iter_state *state)
117{
118	state->iov_offset = iter->iov_offset;
119	state->count = iter->count;
120	state->nr_segs = iter->nr_segs;
121}
122
123static inline bool iter_is_ubuf(const struct iov_iter *i)
124{
125	return iov_iter_type(i) == ITER_UBUF;
126}
127
128static inline bool iter_is_iovec(const struct iov_iter *i)
129{
130	return iov_iter_type(i) == ITER_IOVEC;
131}
132
133static inline bool iov_iter_is_kvec(const struct iov_iter *i)
134{
135	return iov_iter_type(i) == ITER_KVEC;
136}
137
138static inline bool iov_iter_is_bvec(const struct iov_iter *i)
139{
140	return iov_iter_type(i) == ITER_BVEC;
141}
142
143static inline bool iov_iter_is_discard(const struct iov_iter *i)
144{
145	return iov_iter_type(i) == ITER_DISCARD;
146}
147
148static inline bool iov_iter_is_folioq(const struct iov_iter *i)
149{
150	return iov_iter_type(i) == ITER_FOLIOQ;
151}
152
153static inline bool iov_iter_is_xarray(const struct iov_iter *i)
154{
155	return iov_iter_type(i) == ITER_XARRAY;
156}
157
158static inline unsigned char iov_iter_rw(const struct iov_iter *i)
159{
160	return i->data_source ? WRITE : READ;
161}
162
163static inline bool user_backed_iter(const struct iov_iter *i)
164{
165	return iter_is_ubuf(i) || iter_is_iovec(i);
166}
167
168/*
169 * Total number of bytes covered by an iovec.
170 *
171 * NOTE that it is not safe to use this function until all the iovec's
172 * segment lengths have been validated.  Because the individual lengths can
173 * overflow a size_t when added together.
174 */
175static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
176{
177	unsigned long seg;
178	size_t ret = 0;
179
180	for (seg = 0; seg < nr_segs; seg++)
181		ret += iov[seg].iov_len;
182	return ret;
183}
184
185void iov_iter_advance(struct iov_iter *i, size_t bytes);
186void iov_iter_revert(struct iov_iter *i, size_t bytes);
187size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
188size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t bytes);
189size_t iov_iter_single_seg_count(const struct iov_iter *i);
190size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
191			 struct iov_iter *i);
192size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
193			 struct iov_iter *i);
194size_t copy_folio_from_iter_atomic(struct folio *folio, size_t offset,
195		size_t bytes, struct iov_iter *i);
196
197size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
198size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
199size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
200
201static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset,
202		size_t bytes, struct iov_iter *i)
203{
204	return copy_page_to_iter(&folio->page, offset, bytes, i);
205}
206
207static inline size_t copy_folio_from_iter(struct folio *folio, size_t offset,
208					  size_t bytes, struct iov_iter *i)
209{
210	return copy_page_from_iter(&folio->page, offset, bytes, i);
211}
212
213size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
214				 size_t bytes, struct iov_iter *i);
215
216static __always_inline __must_check
217size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
218{
219	if (check_copy_size(addr, bytes, true))
220		return _copy_to_iter(addr, bytes, i);
221	return 0;
222}
223
224static __always_inline __must_check
225size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
226{
227	if (check_copy_size(addr, bytes, false))
228		return _copy_from_iter(addr, bytes, i);
229	return 0;
230}
231
232static __always_inline __must_check
233bool copy_to_iter_full(const void *addr, size_t bytes, struct iov_iter *i)
234{
235	size_t copied = copy_to_iter(addr, bytes, i);
236	if (likely(copied == bytes))
237		return true;
238	iov_iter_revert(i, copied);
239	return false;
240}
241
242static __always_inline __must_check
243bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
244{
245	size_t copied = copy_from_iter(addr, bytes, i);
246	if (likely(copied == bytes))
247		return true;
248	iov_iter_revert(i, copied);
249	return false;
250}
251
252static __always_inline __must_check
253size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
254{
255	if (check_copy_size(addr, bytes, false))
256		return _copy_from_iter_nocache(addr, bytes, i);
257	return 0;
258}
259
260static __always_inline __must_check
261bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
262{
263	size_t copied = copy_from_iter_nocache(addr, bytes, i);
264	if (likely(copied == bytes))
265		return true;
266	iov_iter_revert(i, copied);
267	return false;
268}
269
270#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
271/*
272 * Note, users like pmem that depend on the stricter semantics of
273 * _copy_from_iter_flushcache() than _copy_from_iter_nocache() must check for
274 * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
275 * destination is flushed from the cache on return.
276 */
277size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
278#else
279#define _copy_from_iter_flushcache _copy_from_iter_nocache
280#endif
281
282#ifdef CONFIG_ARCH_HAS_COPY_MC
283size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
284#else
285#define _copy_mc_to_iter _copy_to_iter
286#endif
287
288size_t iov_iter_zero(size_t bytes, struct iov_iter *);
289unsigned long iov_iter_alignment(const struct iov_iter *i);
290unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
291void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov,
292			unsigned long nr_segs, size_t count);
293void iov_iter_kvec(struct iov_iter *i, unsigned int direction, const struct kvec *kvec,
294			unsigned long nr_segs, size_t count);
295void iov_iter_bvec(struct iov_iter *i, unsigned int direction, const struct bio_vec *bvec,
296			unsigned long nr_segs, size_t count);
297void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
298void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction,
299			  const struct folio_queue *folioq,
300			  unsigned int first_slot, unsigned int offset, size_t count);
301void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
302		     loff_t start, size_t count);
303ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
304			size_t maxsize, unsigned maxpages, size_t *start);
305ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
306			size_t maxsize, size_t *start);
307int iov_iter_npages(const struct iov_iter *i, int maxpages);
308void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state);
309
310const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags);
311
312static inline size_t iov_iter_count(const struct iov_iter *i)
313{
314	return i->count;
315}
316
317/*
318 * Cap the iov_iter by given limit; note that the second argument is
319 * *not* the new size - it's upper limit for such.  Passing it a value
320 * greater than the amount of data in iov_iter is fine - it'll just do
321 * nothing in that case.
322 */
323static inline void iov_iter_truncate(struct iov_iter *i, u64 count)
324{
325	/*
326	 * count doesn't have to fit in size_t - comparison extends both
327	 * operands to u64 here and any value that would be truncated by
328	 * conversion in assignement is by definition greater than all
329	 * values of size_t, including old i->count.
330	 */
331	if (i->count > count)
332		i->count = count;
333}
334
335/*
336 * reexpand a previously truncated iterator; count must be no more than how much
337 * we had shrunk it.
338 */
339static inline void iov_iter_reexpand(struct iov_iter *i, size_t count)
340{
341	i->count = count;
342}
343
344static inline int
345iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
346{
347	size_t shorted = 0;
348	int npages;
349
350	if (iov_iter_count(i) > max_bytes) {
351		shorted = iov_iter_count(i) - max_bytes;
352		iov_iter_truncate(i, max_bytes);
353	}
354	npages = iov_iter_npages(i, maxpages);
355	if (shorted)
356		iov_iter_reexpand(i, iov_iter_count(i) + shorted);
357
358	return npages;
359}
360
361struct iovec *iovec_from_user(const struct iovec __user *uvector,
362		unsigned long nr_segs, unsigned long fast_segs,
363		struct iovec *fast_iov, bool compat);
364ssize_t import_iovec(int type, const struct iovec __user *uvec,
365		 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
366		 struct iov_iter *i);
367ssize_t __import_iovec(int type, const struct iovec __user *uvec,
368		 unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
369		 struct iov_iter *i, bool compat);
370int import_ubuf(int type, void __user *buf, size_t len, struct iov_iter *i);
371
372static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
373			void __user *buf, size_t count)
374{
375	WARN_ON(direction & ~(READ | WRITE));
376	*i = (struct iov_iter) {
377		.iter_type = ITER_UBUF,
378		.data_source = direction,
379		.ubuf = buf,
380		.count = count,
381		.nr_segs = 1
382	};
383}
384/* Flags for iov_iter_get/extract_pages*() */
385/* Allow P2PDMA on the extracted pages */
386#define ITER_ALLOW_P2PDMA	((__force iov_iter_extraction_t)0x01)
387
388ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages,
389			       size_t maxsize, unsigned int maxpages,
390			       iov_iter_extraction_t extraction_flags,
391			       size_t *offset0);
392
393/**
394 * iov_iter_extract_will_pin - Indicate how pages from the iterator will be retained
395 * @iter: The iterator
396 *
397 * Examine the iterator and indicate by returning true or false as to how, if
398 * at all, pages extracted from the iterator will be retained by the extraction
399 * function.
400 *
401 * %true indicates that the pages will have a pin placed in them that the
402 * caller must unpin.  This is must be done for DMA/async DIO to force fork()
403 * to forcibly copy a page for the child (the parent must retain the original
404 * page).
405 *
406 * %false indicates that no measures are taken and that it's up to the caller
407 * to retain the pages.
408 */
409static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter)
410{
411	return user_backed_iter(iter);
412}
413
414struct sg_table;
415ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t len,
416			   struct sg_table *sgtable, unsigned int sg_max,
417			   iov_iter_extraction_t extraction_flags);
418
419#endif